1. Field of the Invention
This invention relates to a pump and valve apparatus that provides a reliable valve opening and closing operation with improved durability.
2. Description of the Prior Art
Pumps in use include reciprocating pumps in which the reciprocating action of a piston is used to open and close a valve and pressure-feed a fluid such as water, for example. Such reciprocating pumps are divided into three types according to the form of piston used: the bucket type, the plunger type and the piston type.
As shown in FIG. 12, bucket type pumps have a hole 102 in the piston 101 that slides in a cylinder 100. The hole 102 and the cylinder outlet 103 are provided with respective valves 104 and 105. The piston 101 is caused to move reciprocally via a piston rod 106. The descent of the piston 101 opens the valve 104 and closes valve 105, drawing water through the hole 102 to the upper part of the cylinder 100. This water in the upper part of the cylinder 100 is then sent out under pressure by the rise of the piston 101.
Plunger type pumps, such as shown in FIG. 13, are generally used for high-pressure applications. Water, for example, in the cylinder 107 is forced under pressure out of the cylinder outlet 108' by the insertion of the plunger 108 into the cylinder 107.
FIG. 14 shows a piston type pump in which the movement of a piston 111 driven by a crank mechanism 109 inside a cylinder 110 opens and closes valves 112 and 113 to feed out the water under pressure.
These types of reciprocating pumps use various types of packing, for example rubber, to obtain a watertight seal between the piston and the cylinder. In the bucket type pump, packing is provided between the cylinder 100 and the piston rod 106, and in the plunger type pump the cylinder 107 and plunger, 108 are each provided with a packing therebetween. On the piston type pumps, piston rings are provided around the circumference of the piston 111.
When these types of conventional reciprocating pumps, especially plunger type pumps, are used to pump fluids containing granular material, such as in a cement mill, the motion of the plunger is accompanied by a rubbing of the particles against the packing, which causes the packing to wear rapidly. This has necessitated replacing packings at short intervals, which reduces operating efficiency and shortens the working life of the pump itself. On piston pumps, the piston rings wear and can cause damage to the internal surface of the cylinder.
Various types of valves are used as means of limiting or controlling the fluid flow. FIGS. 8 and 9 show a valve device used on plunger type pumps which are well-known as pumps for high-pressure applications. These valve devices are comprised of a tubular valve seat 50, a valve-piece 52 provided with a surrounding flange 51, and a valve spring 53 which presses the valve-piece 52 towards the valve seat 50. With plunger type pumps used to pump materials such as cement clinker, for example, as the valve-piece 52 of the conventional valve devices opens and closes, solid bodies contained in the fluid can be caught between the valve-piece 52 and the valve seat 50.
Because the valve seats 50 used in conventional valve devices are tubular members, solid bodies readily pass therethrough, in addition to which as the valve seat 50 and the valve-piece 52 are made of metal, the valve operation is not always reliable if solid bodies are caught therebetween. This can make it impossible to pump constant quantities of fluid at fixed intervals, so use of the pump was accompanied by a lowering of the operating efficiency. Furthermore, solid bodies caught between the valve seat 50 and the valve-piece 52 could cause damage to the seat and valve-piece, resulting in fluid leaking out of the gap between them. Conventionally, therefore, the valve device has had to be replaced at this point, interrupting operations.